{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,21]],"date-time":"2026-07-21T09:06:41Z","timestamp":1784624801335,"version":"3.55.0"},"reference-count":40,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2026,7,18]],"date-time":"2026-07-18T00:00:00Z","timestamp":1784332800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Biomolecules"],"abstract":"<jats:p>Anthracyclines such as doxorubicin (DOX) remain central components of breast cancer (BC) chemotherapy, although their efficacy is frequently limited by drug resistance. Myoglobin (MB), an oxygen-binding heme protein expressed in breast tumors, has been implicated in the detoxification of DOX in cardiomyocytes, but its role in BC remains unclear. Using MB-expressing and MB-knockout (MBKO) MDA-MB-468 BC cells, we demonstrate that MB confers hypoxia-dependent resistance to DOX. Under hypoxia, MB-expressing cells exhibited reduced intracellular DOX-associated fluorescence, enhanced superoxide generation, and decreased sensitivity to DOX, findings consistent with altered redox cycling and oxidative processing of the drug. Re-expression of MB in MBKO cells restored resistance, whereas pharmacological modulation of MB function using carbon monoxide-releasing molecule-3 and tert-butoxycarbonyl-alanine reversed MB-dependent reductions in intracellular DOX accumulation. In contrast, aclarubicin, an anthracycline lacking the hydroquinone moiety required for efficient redox cycling, failed to reproduce MB-dependent effects. Analyses of four independent neoadjuvant BC cohorts further demonstrated that elevated MB expression was consistently associated with reduced probability of achieving pathological complete response following anthracycline-containing chemotherapy. Collectively, these findings identify MB as a previously unrecognized modulator of BC response to redox-active anthracyclines and support its potential utility as both a predictive biomarker and therapeutic target.<\/jats:p>","DOI":"10.3390\/biom16071055","type":"journal-article","created":{"date-parts":[[2026,7,20]],"date-time":"2026-07-20T00:47:32Z","timestamp":1784508452000},"page":"1055","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Role of Endogenous Myoglobin in Anthracycline Response in Breast Cancer"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-4871-9922","authenticated-orcid":false,"given":"Ilona","family":"Rybinska","sequence":"first","affiliation":[{"name":"Department of Medical Biotechnology and Translational Medicine, University of Milan, 20133 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Andreas","family":"Petry","sequence":"additional","affiliation":[{"name":"Experimental and Molecular Pediatric Cardiology, German Heart Center, TUM University Hospital, Technical University of Munich, 80636 Munich, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Thomas","family":"Hankeln","sequence":"additional","affiliation":[{"name":"Institute of Organismic and Molecular Evolution, Molecular Genetics and Genome Analysis, Johannes Gutenberg University, 55128 Mainz, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6023-4234","authenticated-orcid":false,"given":"Thomas A.","family":"Gorr","sequence":"additional","affiliation":[{"name":"Department of Veterinary Physiology, University of Zurich, CH-8057 Zurich, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8147-4720","authenticated-orcid":false,"given":"Gaetano","family":"Cairo","sequence":"additional","affiliation":[{"name":"Department of Biomedical Sciences for Health, University of Milan, 20133 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,7,18]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"GBD 2023 Breast Cancer Collaborators (2026, May 20). Global, Regional, and National Burden of Breast Cancer Among Females, 1990\u20132023, with Forecasts to 2050: A Systematic Analysis for the Global Burden of Disease Study 2023\u2014The Lancet Oncology. Available online: https:\/\/www.thelancet.com\/journals\/lanonc\/article\/PIIS1470-2045(25)00730-2\/abstract.","DOI":"10.2139\/ssrn.5533924"},{"key":"ref_2","unstructured":"(2026, May 06). Liposomal Doxorubicin Market|Global Market Analysis Report\u20142035. Available online: https:\/\/www.factmr.com\/report\/liposomal-doxorubicin-market."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"6550","DOI":"10.21037\/tcr-24-1129","article-title":"Targeting Breast Cancer Resistance Protein (BCRP\/ABCG2) in Cancer","volume":"13","author":"Chen","year":"2024","journal-title":"Transl. Cancer Res."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"102","DOI":"10.1007\/s13346-024-01648-0","article-title":"A Comprehensive Review on Doxorubicin: Mechanisms, Toxicity, Clinical Trials, Combination Therapies and Nanoformulations in Breast Cancer","volume":"15","author":"Bisht","year":"2025","journal-title":"Drug. Deliv. Transl. Res."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"338","DOI":"10.1038\/s41419-022-04783-z","article-title":"Identification of a Novel Mechanism for Reversal of Doxorubicin-Induced Chemotherapy Resistance by TXNIP in Triple-Negative Breast Cancer via Promoting Reactive Oxygen-Mediated DNA Damage","volume":"13","author":"Chen","year":"2022","journal-title":"Cell Death Dis."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"18181","DOI":"10.1038\/s41598-024-65508-0","article-title":"Piperine Enhances Doxorubicin Sensitivity in Triple-Negative Breast Cancer by Targeting the PI3K\/Akt\/mTOR Pathway and Cancer Stem Cells","volume":"14","author":"Hakeem","year":"2024","journal-title":"Sci. Rep."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"109138","DOI":"10.1016\/j.cbi.2020.109138","article-title":"Can Image Analysis Provide Evidence That Lysosomal Sequestration Mediates Daunorubicin Resistance?","volume":"327","author":"Mlejnek","year":"2020","journal-title":"Chem.-Biol. Interact."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Sil, R., and Chakraborti, A.S. (2025). Major Heme Proteins Hemoglobin and Myoglobin with Respect to Their Roles in Oxidative Stress\u2014A Brief Review. Front. Chem., 13.","DOI":"10.3389\/fchem.2025.1543455"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1736","DOI":"10.1038\/sj.bjc.6605702","article-title":"Endogenous Myoglobin in Human Breast Cancer Is a Hallmark of Luminal Cancer Phenotype","volume":"102","author":"Kristiansen","year":"2010","journal-title":"Br. J. Cancer"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"201","DOI":"10.2353\/ajpath.2009.081124","article-title":"Expression and Functional Regulation of Myoglobin in Epithelial Cancers","volume":"175","author":"Flonta","year":"2009","journal-title":"Am. J. Pathol."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"185","DOI":"10.1124\/pr.56.2.6","article-title":"Anthracyclines: Molecular Advances and Pharmacologic Developments in Antitumor Activity and Cardiotoxicity","volume":"56","author":"Minotti","year":"2004","journal-title":"Pharmacol. Rev."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"408","DOI":"10.1124\/jpet.107.122820","article-title":"Doxorubicin Degradation in Cardiomyocytes","volume":"322","author":"Menna","year":"2007","journal-title":"J. Pharmacol. Exp. Ther."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Finn, N.A., Findley, H.W., and Kemp, M.L. (2011). A Switching Mechanism in Doxorubicin Bioactivation Can Be Exploited to Control Doxorubicin Toxicity. PLoS Comput. Biol., 7.","DOI":"10.1371\/journal.pcbi.1002151"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"5088","DOI":"10.1074\/jbc.M306568200","article-title":"Oxidative Degradation of Cardiotoxic Anticancer Anthracyclines to Phthalic Acids: Novel Function for Ferrylmyoglobin","volume":"279","author":"Cartoni","year":"2004","journal-title":"J. Biol. Chem."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"9","DOI":"10.1038\/s41514-024-00135-7","article-title":"A Review of the Pathophysiological Mechanisms of Doxorubicin-Induced Cardiotoxicity and Aging","volume":"10","author":"Linders","year":"2024","journal-title":"npj Aging"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"44735","DOI":"10.1038\/srep44735","article-title":"Doxorubicin Induces Cardiotoxicity through Upregulation of Death Receptors Mediated Apoptosis in Cardiomyocytes","volume":"7","author":"Zhao","year":"2017","journal-title":"Sci. Rep."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Aboouf, M.A., Armbruster, J., Thiersch, M., Guscetti, F., Kristiansen, G., Schraml, P., Bicker, A., Petry, R., Hankeln, T., and Gassmann, M. (2022). Pro-Apoptotic and Anti-Invasive Properties Underscore the Tumor-Suppressing Impact of Myoglobin on a Subset of Human Breast Cancer Cells. Int. J. Mol. Sci., 23.","DOI":"10.1101\/2022.06.30.498102"},{"key":"ref_18","unstructured":"Wittenberg, B.A., and Wittenberg, J.B. (1993). Effects of Carbon Monoxide on Isolated Heart Muscle Cells. Res. Rep. Health Eff. Inst., 1\u201312; discussion 13\u201321."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1112","DOI":"10.1038\/nprot.2006.179","article-title":"Sulforhodamine B Colorimetric Assay for Cytotoxicity Screening","volume":"1","author":"Vichai","year":"2006","journal-title":"Nat. Protoc."},{"key":"ref_20","first-page":"432","article-title":"Fluorescence-Based Assays for Measuring Doxorubicin in Biological Systems","volume":"2","author":"Kauffman","year":"2016","journal-title":"React. Oxyg. Species"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"56","DOI":"10.1089\/ars.2017.7482","article-title":"Stabilization of P22phox by Hypoxia Promotes Pulmonary Hypertension","volume":"30","author":"Zhang","year":"2018","journal-title":"Antioxid. Redox Signal."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"929","DOI":"10.1038\/sj.bjc.6605893","article-title":"Erratum: Large Meta-Analysis of Multiple Cancers Reveals a Common, Compact and Highly Prognostic Hypoxia Metagene","volume":"103","author":"Buffa","year":"2010","journal-title":"Br. J. Cancer"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"100764","DOI":"10.1016\/j.xgen.2025.100764","article-title":"Defining Hypoxia in Cancer: A Landmark Evaluation of Hypoxia Gene Expression Signatures","volume":"5","author":"Hartley","year":"2025","journal-title":"Cell Genom."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"105923","DOI":"10.1016\/j.esmoop.2025.105923","article-title":"Pathological Complete Response and Survival after Neoadjuvant Chemotherapy in Patients with Stage I TNBC: A Registry-Based Study","volume":"10","author":"Gielen","year":"2025","journal-title":"ESMO Open"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Armbruster, J., Aboouf, M.A., Gassmann, M., Egert, A., Schorle, H., Hornung, V., Schmidt, T., Schmid-Burgk, J.L., Kristiansen, G., and Bicker, A. (2024). Correction: Myoglobin Regulates Fatty Acid Trafficking and Lipid Metabolism in Mammary Epithelial Cells. PLoS ONE, 19.","DOI":"10.1371\/journal.pone.0316741"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"1077","DOI":"10.1096\/fsb2fj000497fje","article-title":"Myoglobin Facilitates Oxygen Diffusion","volume":"15","author":"Merx","year":"2001","journal-title":"FASEB J."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"2342","DOI":"10.1089\/ars.2012.4887","article-title":"Redox Reactions of Myoglobin","volume":"18","author":"Richards","year":"2013","journal-title":"Antioxid. Redox Signal."},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Popovi\u0107, D.M., Siletsky, S.A., He, C., and Gunner, M.R. (2026). Editorial: Exploration of the Role of Heme Proteins in Biology with Experimental and Computational Methods. Front. Chem., 14.","DOI":"10.3389\/fchem.2026.1810989"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"C302","DOI":"10.1152\/ajpcell.00360.2016","article-title":"Biological Signaling by Carbon Monoxide and Carbon Monoxide-Releasing Molecules","volume":"312","author":"Motterlini","year":"2017","journal-title":"Am. J. Physiol.-Cell Physiol."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"102124","DOI":"10.1016\/j.redox.2021.102124","article-title":"The Potentials of Carbon Monoxide-Releasing Molecules in Cancer Treatment: An Outlook from ROS Biology and Medicine","volume":"46","author":"Vo","year":"2021","journal-title":"Redox Biol."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"1396","DOI":"10.1038\/s41467-019-09111-2","article-title":"Myoglobinopathy Is an Adult-Onset Autosomal Dominant Myopathy with Characteristic Sarcoplasmic Inclusions","volume":"10","author":"Engvall","year":"2019","journal-title":"Nat. Commun."},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Guo, B., Tam, A., Santi, S.A., and Parissenti, A.M. (2016). Role of Autophagy and Lysosomal Drug Sequestration in Acquired Resistance to Doxorubicin in MCF-7 Cells. BMC Cancer, 16.","DOI":"10.1186\/s12885-016-2790-3"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"120","DOI":"10.1186\/s12943-024-02034-7","article-title":"Diversifying the Anthracycline Class of Anti-Cancer Drugs Identifies Aclarubicin for Superior Survival of Acute Myeloid Leukemia Patients","volume":"23","author":"Qiao","year":"2024","journal-title":"Mol. Cancer"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"123","DOI":"10.1007\/s00280-024-04693-1","article-title":"Aclarubicin: Contemporary Insights into Its Mechanism of Action, Toxicity, Pharmacokinetics, and Clinical Standing","volume":"94","author":"Murzyn","year":"2024","journal-title":"Cancer Chemother. Pharmacol."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"2515176","DOI":"10.1080\/2162402X.2025.2515176","article-title":"Potent Immune-Dependent Anticancer Effects of the Non-Cardiotoxic Anthracycline Aclarubicin","volume":"14","author":"Cerrato","year":"2025","journal-title":"Oncoimmunology"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"43417","DOI":"10.1074\/jbc.M111.227553","article-title":"Endogenous Myoglobin in Breast Cancer Is Hypoxia-Inducible by Alternative Transcription and Functions to Impair Mitochondrial Activity","volume":"286","author":"Kristiansen","year":"2011","journal-title":"J. Biol. Chem."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"17588359241309169","DOI":"10.1177\/17588359241309169","article-title":"Predictive Factors for Complete Pathologic Response in Luminal Breast Cancer: Impact of Ki67 and HER2 Low Expression","volume":"16","author":"Miras","year":"2024","journal-title":"Ther. Adv. Med. Oncol."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"361","DOI":"10.1200\/JCO-24-01916","article-title":"Anthracyclines in Early Breast Cancer: The Long Goodbye","volume":"43","author":"Grinda","year":"2025","journal-title":"J. Clin. Oncol."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"7530","DOI":"10.1038\/s41598-023-34614-w","article-title":"Endogenous Myoglobin Expression in Mouse Models of Mammary Carcinoma Reduces Hypoxia and Metastasis in PyMT Mice","volume":"13","author":"Aboouf","year":"2023","journal-title":"Sci. Rep."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"101953","DOI":"10.1016\/j.redox.2021.101953","article-title":"Reactive Oxygen Species Produced by Altered Tumor Metabolism Impacts Cancer Stem Cell Maintenance","volume":"44","author":"Tuy","year":"2021","journal-title":"Redox Biol."}],"container-title":["Biomolecules"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2218-273X\/16\/7\/1055\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,7,21]],"date-time":"2026-07-21T08:52:36Z","timestamp":1784623956000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2218-273X\/16\/7\/1055"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,7,18]]},"references-count":40,"journal-issue":{"issue":"7","published-online":{"date-parts":[[2026,7]]}},"alternative-id":["biom16071055"],"URL":"https:\/\/doi.org\/10.3390\/biom16071055","relation":{},"ISSN":["2218-273X"],"issn-type":[{"value":"2218-273X","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,7,18]]}}}